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To Foraminiferal Abundance and Diversity in an Area of the Eastern Pacific Ocean Licensed for Polymetallic Nodule Exploration fmars-06-00114 March 29, 2019 Time: 18:52 # 1 ORIGINAL RESEARCH published: 02 April 2019 doi: 10.3389/fmars.2019.00114 The Contribution of Fine Sieve Fractions (63–150 mm) to Foraminiferal Abundance and Diversity in an Area of the Eastern Pacific Ocean Licensed for Polymetallic Nodule Exploration Andrew J. Gooday* and Aurélie Goineau National Oceanography Centre, University of Southampton, Waterfront Campus, Southampton, United Kingdom The sieve mesh sizes used in benthic foraminiferal studies exert a strong influence on faunal densities and composition. We examined the consequences of including Edited by: finer (63–150 mm) size classes in a study of Rose Bengal stained (‘live’) and dead Randi D. Rotjan, foraminifera in 5 Megacorer samples (0–1 cm layer) from abyssal sites in the eastern Boston University, United States Clarion-Clipperton Zone (CCZ; equatorial Pacific), a region with commercially significant Reviewed by: Ellen Pape, deposits of polymetallic nodules. More than 60% of intact specimens originated from Ghent University, Belgium the finer (<150 mm) fractions, with over half being picked from 63 to 125 mm residues. Akkur Vasudevan Raman, Test fragments, mainly agglutinated tubes, were also abundant but were more evenly Andhra University, India distributed between coarser and finer residues. The two fractions yielded the same *Correspondence: Andrew J. Gooday main groups (a mixture of formal taxa and informal groupings) and were dominated [email protected] by single-chambered forms (‘monothalamids’), the majority undescribed. Some were disproportionately abundant in finer fractions: rotaliids in the stained (‘live’), textulariids in Specialty section: This article was submitted to the dead, and trochamminids, Lagenammina spp., Nodellum-like forms, saccamminids Deep-Sea Environments and Ecology, and spheres in both assemblages. However, the most striking difference was the much a section of the journal Frontiers in Marine Science greater abundance of tiny, largely undescribed spherical agglutinated morphotypes in Received: 05 October 2018 the <150-mm fractions. Our 5 samples yielded 462 morphospecies, of which 313 Accepted: 25 February 2019 occurred in <150-mm fraction and 170 were confined to this fraction. Twelve of the Published: 02 April 2019 31 top-ranked species in the stained assemblage were more or less limited (>90%) to Citation: the finer fractions; the corresponding number for the stained C dead assemblage was Gooday AJ and Goineau A (2019) The Contribution of Fine Sieve 12 out of 35. Of the 46 most abundant species in the stained C dead assemblage, Fractions (63–150 µm) 35 were monothalamids (mainly spheres, Lagenammina spp., Nodellum-like forms, and to Foraminiferal Abundance and Diversity in an Area of the Eastern saccamminids), the remainder being rotaliids (3), hormosinids (3), trochamminids (3) and Pacific Ocean Licensed textulariids (2). By far the most abundant species overall, a tiny agglutinated sphere, for Polymetallic Nodule Exploration. was almost entirely confined to the finer fractions. Although small foraminifera that pass Front. Mar. Sci. 6:114. doi: 10.3389/fmars.2019.00114 through a 150-mm screen are time-consuming to analyze, they constitute an important Frontiers in Marine Science | www.frontiersin.org 1 April 2019 | Volume 6 | Article 114 fmars-06-00114 March 29, 2019 Time: 18:52 # 2 Gooday and Goineau Foraminifera in Fine Sieve Fractions part of abyssal Pacific assemblages and may include opportunistic species that respond to episodic food pulses as well as pioneer recolonizers of defaunated substrates. It is therefore important to consider them in studies of possible mining impacts on abyssal benthic communities. Keywords: polymetallic nodules, Clarion-Clipperton Zone, baseline survey, abyssal benthic foraminifera, sieve mesh size, biodiversity, recolonization INTRODUCTION areas, also in the eastern CCZ, licensed by the International Seabed Authority for seabed exploration to the UK Seabed The use of different sized meshes to sieve sediment samples is an Resources Ltd. (UK-1 area), and Ocean Mineral Singapore Pte important issue in meiofaunal research, the mesh acting as a filter Ltd. (OMS area). The UK-1 area was sampled in 2013 and that strongly influences important assemblage metrics, notably both areas were sampled in 2015 during ABYSSLINE research faunal densities, biomass, diversity and taxonomic composition cruises. Previous studies on meiofaunal foraminifera within of taxa such as nematodes (Leduc et al., 2010). A mesh size the framework of this project have described novel species of 32 mm is now the widely accepted lower limit for the that use radiolarian shells as microhabitats (Goineau and metazoan meiofauna. In the case of foraminifera, however, Gooday, 2015) and foraminiferal composition and diversity different studies have used a variety of different sized meshes in >150 mm size fractions (Goineau and Gooday, 2017). Here, (Sen Gupta et al., 1987). The most common are 150, 125, and we extend this earlier research by describing assemblages of 63 mm, although larger (250 or 300 mm; e.g., Bernstein et al., stained and dead benthic foraminifera retained on 63 and 1978; Lutze and Coulbourne, 1984; Gooday et al., 2001) or smaller 125 mm mesh sieves and comparing them with assemblages in (45 or 32 mm; e.g., Gooday, 1986; Pawlowski and Lapierre, residues >150 mm. We address two main questions. (1) How 1988; Pawlowski, 1991; Gooday et al., 1995; Nozawa et al., much information on foraminiferal abundance and diversity 2006; Szarek et al., 2007) sizes have been adopted occasionally. is added by analyzing these finer fractions? (2) What are the The need to analyze finer sieve fractions (63–125 mm or 63– differences in foraminiferal assemblage composition between the 150 mm) becomes more pressing in deep-sea settings, where larger and smaller size fractions? benthic organisms are generally small in size compared to shallower waters (Thiel, 1975, 1983; Shirayama and Horikoshi, 1989). Although this involves a larger investment of time MATERIALS AND METHODS compared to the analysis of larger-sized fractions, Schröder et al. (1987) argue that the extra effort is worthwhile because valuable General information about the ABYSSLINE project is given by faunal information, including a large proportion of specimens Glover et al. (2015). For environmental information about the belonging to environmentally important ‘indicator’ species, is study area see Amon et al. (2016) and Goineau and Gooday lost by ignoring sieve residues <150 mm. For example, at (2017). Pape et al. (2017) provide further environmental data bathyal depths in the North Atlantic, small-sized species include (sediment granulometry, porosity and sorting, total organic several that respond opportunistically to seasonally pulsed food carbon and total nitrogen content) for the GSR license area, inputs (Gooday and Hughes, 2002; Duchemin et al., 2007; located to the west of the UK-1 and OMS areas and in somewhat Phipps et al., 2012). deeper water (∼4500 m). In general terms, our shipboard and Relatively few studies based on fine sieve fractions have been laboratory methods followed those described by Goineau and undertaken in the Pacific Ocean. Snider et al. (1984) analyzed Gooday (2017). We use the term ‘stained’ to refer to specimens the 45–150 and 150–300 mm fractions for meiofaunal organisms, that were inferred to be alive when stained. mainly foraminifera, many of them single-chambered forms (monothalamids). More recently, Nozawa et al. (2006) used Sampling a 32 mm mesh in a study of foraminifera, again dominated Samples were collected during two ABYSSLINE cruises at 5 sites by monothalamids, from the ‘Kaplan East’ site in the eastern (Supplementary Table S1) in three 30 × 30 km study areas Clarion-Clipperton Zone (CCZ, abyssal equatorial Pacific), (‘strata’) located within the UK-1 and OMS exploration contract a region where large tracts of seafloor are covered with areas (Figure 1). Two were obtained in Stratum A of the UK-1 commercially significant deposits of polymetallic nodules. license area, centered around 13◦490 N, 116◦360 W, during the Radziejewska et al. (2006) presented some preliminary first cruise (AB01, R/V Melville, cruise MV1313, 3–27 October observations of monothalamids and other foraminifera based 2013), two in UK-1 Stratum B, centered around 12◦ 28.90 N, 116◦ on the >32-mm fractions of samples from the same general 36.30 W, and one in the OMS Stratum, centered around 12◦ 8.20 area. Ohkawara et al. (2009) described a tiny new spherical N, 117◦ 17.70 W during the second cruise (AB02: R/V Thomas monothalamid that was abundant in samples from the Kaplan G Thompson cruise TN319; 12 February to 25 March, 2015). Central site in the deeper and more central part of the CCZ. In each case the samples were recovered using a hydraulically The present contribution is part of the AYSSLINE (ABYSSal dampened Megacorer (BCMEGA OSIL Bowers & Connelly type), baseLINE) project, a baseline survey of foraminifera in two equipped with 12 polycarbonate coring tubes. As soon as possible Frontiers in Marine Science | www.frontiersin.org 2 April 2019 | Volume 6 | Article 114 fmars-06-00114 March 29, 2019 Time: 18:52 # 3 Gooday and Goineau Foraminifera in Fine Sieve Fractions FIGURE 1 | (Left) Location of the Ocean Mineral Singapore (OMS) and UK-1 exploration contract areas in the eastern Clarion-Clipperton Zone, equatorial Pacific. (Right) Location of UK-1 Strata A and B and the OMS stratum within the two contract areas. after collection, the cores were sliced, using a metal plate, into observations of test morphology and wall structure, and assigned 0.5-cm thick layers to 2 cm depth and 1-cm thick layers from to genera or species where possible. Those that could not be 2 to 10 cm depth and each layer preserved separately in a placed in known taxa were given a descriptive working name. 500 ml plastic bottle with 10% formalin buffered with borax. Any Some of the methodological challenges involved in analyzing nodules present in the core were carefully removed in order to benthic foraminifera in sediment residues from the abyssal CCZ facilitate slicing and sediment adhering to them washed into the are outlined in the Supplementary Material.
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